Tunnel kiln



May 18 1926.

P. A. MEI-:HAN ET AL TUNNEL KILN Original Filed June 30. 1922 2 Sheets-Sheet l ez'p/I TTORNE Y May 18 1926.

P. A. MEEHAN ET AL TUNNEL KILN original Filed June 50. 1922 2 Sheets-Sheet 2 /NVENTO/e 00m@ l Ma/40 an Mk A ORA/EY Patented May 18, 1926.

f STAT PAUL A. MEEHAN AND HARRY M. ROBERTSON', OF CLEVELAND, OHIO, ASSIGNORS T0 AMERICAN DBESSLER TUNNEL KILNS, INC., OF CLEVELAND, OHIO, l COIZEEGIRHA TION 0F NEW YORK.

TUNNEL IKILN.

Application tiled June 80, 1922, Serial No. 571,976. Renewed September 30, 1925.

Our present invention relates to continuous tunnel kilns for use in the heat treatment of material which needs to be exposed for a considerable period of time tohigh'temperatures and needs to be stirred continuously or at frequent intervals during such exposure and our present invention was de vise with the general object of providingsimple and effective means for suitably stirring the material during its passage through the ki'ln.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specication. Fora better understanding of our invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings in which we have illustrated and described preferred embodiments of our invention.

Of the drawings:

Fig. 1 is a plan ofa kiln equipped with our invention; Y v

Fig. 2 is a sectional elevation on the line 2-2 of Fig. 1; t

Fig. 3 is a transverse section 0n the line 3--3 of Fig. 1;

Fig. 4 is a view taken similarly to Fig. 3 illustrating a modified form of stirrer;

Fig. 5 is a view taken similarly to Fig. 3 illustrating another form of stirring mechanism;

Fig. 6 is a section on the line 6-6 of Fig. 5; and

Fig. 7 is a partial section on of Fig. 6.

In the drawings, and referring first to the construction shown in Figs. 1, 2, and 3, we have illustrated the use of our invention in a continuous tunnel kiln of the well known the line 7-7 Dressler type in which the kiln chamber is heated by combustion chambers B longitudinally disposed in the kiln chamber at opposite sides of the goods pathway and extending'iii the particular kiln shown practically the entire length of the kiln.

Adjacent one end, each combustion chamber is provided with a distributed set of burner inlets C, and at their opposite ends the combustion chambers are provided with outlets l) connected by the conduit D to a suitable draft creating device such as the able refractory material, and is formed at f its upperside with a trough shaped cavity H. This cavity extends longitudinally of the car, and the cavities of the different cars in the kiln unite to form a continuous trough-like receptacle for the material treated which extends the full length of the kiln. To facilitate the heating of the material open ended transverse channels G' are advantageously formed in the car structure between 'the refractory body portion proper and the material receiving platform. The usual cooling pipes F', or the like may be employed to cool the metallic under-portions of the cars.

Uur invention is capable of use in various ways and for treating various forms of material. The particular construction illustrated in Figs. l, 2 and 3 wasprimarily devised, and is especially adapted for use in preparing a base material for the manufacture of bicarbonate of soda, by heating a mixture of lime, soda ash and chrome"I iron ore to a temperature of approximately 2200o F. and subjecting the material to an oxidizing action at this temperature.

In the preferred contemplated mode of operation, the cars G are inserted into the kiln, one at a time, in the usual manner from a transfer car or tube J and preferably the cai's are quite hot when inserted. The cars Gr are empty when inserted, and each car after being in the kiln for a period corresponding to its movement of one or two car lengths and correspondingly heated is charged through a charging funnel L mounted in the roof of the kiln. Each car after passing through the kiln is received by a car transfer K, and is then returned to the transfer -table J along the return track I, and is reinserted in the kiln. The treated material is raked od' each car outside of the kiln at any suitable point along the path traversed by the cars. Preferably the period between the removal of a car from the kiln at the exit end of the'latter, and its reinsertion into the entrance end of the kiln is made quite short so that the car will not cool oi much while out of the kiln.

Forthe effective heat treatment and oxi- (lation of the material it is unnecessary to stir the latter as it passes through the kiln. This stirring of the material is accomplished in the apparatus shown in Figs. 1, 2, and 3 by means of a plurality of sets of stationary plows M distributed along the length of the kiln. These plows M are formed of metal and as shown in Figs. 1, 9, and 3, the plows M of each set are secured to a corresponding metallic yoke member N, the legs of which extend through the roof of the kiln. Each yoke member N is hollow to -rcceive a coolingluid such as water. As indicated by the arrows in Fig. 3, the hollow interiors of the various yokes N are connected to a water circulating piping system comprising pipes O running longitudinally of the kiln. The plows M extend down into the material nearly to the bottom of the trough H', and each set of plows extend across the width of the trough, so that. as the cars move slowly past the plows M, the material is constantly being agitated, and has fresh surfaces exposed to the kiln atmosphere. The cooling of the plow supporting yokes N, and thereby of the plows M by the circulation of water through the yokes N, enables the plows and supports to stand up under the severe condition of operation to which they are subjected.

It will be apparent, of course, that many modifications may be made in the form of the stirring provisions employed, and in Fig. 4 we have illustrated a modification in which each plow MA is made hollow, and is secured to the lower end of a tubular post M1o projecting down through the roof of the kiln. Axially disposed within each tubular post h 1 is a circulation pipe h 15 of smaller external diameter than the bore of the post. As shown clearly in Fig. 4, the posts M1 and pipes M1s for each set of plows MA, are connected between cooling water supply and discharge ipes O1 and O11, so that the cooling water ows down through each pipe M11 into the cavity of the corresponding plow MA, and then flows up through the space between the pipe M15 and the wall of the hollow post M1.

To avoid the necessity 'of water cooling the stirrers we may insert the stirrers into the kiln, and remove them therefrom at suiciently frequently intervals, and for suflicientl short periods of time to thereby proper y stir the material without heating the stirrers up to a destructive temperature. One arrangement for this purpose 1s shown in Figs. 5, 6 and 7, wherein the kiln AAj shown and the cars employed may be similar to those shown in Figs. l, 2 and 3 exceept that openings A are formed in the roof of the kiln at frequent intervals along the length of the latter. These openingspermit the insertion and removal of stirrers R. When the latter are out of the kiln chamber the openings A are closed as by means of the doors Q. Each stirrer R as shown in Figs. 5, 6, and 7 is in the form of a rotary head carried by a vertically disposed stem S which is longitudinally and rotatably movable. As shown each stem S is externally corrugated to provide circular gear teeth in mesh with gear wheels lV and lV. The gear wheels W are mounted on a driving shaft X which extends lengthwise of the kiln and may be rotated first in one direction and then in the other by a suitable motor or other driving device not shown). The gears WV are idlers opposed to the gears lV, and forming roller guides for the stems S. Each stem S is tubular and is splined on a corresponding vertically disposed driving shaft T. Each shaft T is provided at its upper end with a bevel gear T in mesh with a corresponding bevel gear carried by a driving shaft U running longitudinally of the kiln and rotated by a suitable motor or other driving device (not shown). Each stirrer R is mounted in a corresponding supporting frame 1, shown as a metallic yoke supported on beams 7" carried by the kiln huckstays.y

In the intended operation of the form of our invention shown in Figs.' 5, 6, and 7, the doors Q are opened at intervals to permit the insertion into the kiln chambers of stirrers R which'are lowered into place by rotating the gears XV in a counter clockwise direction. The shaft U may rotate continuously and in any event is rotated as the stirrers are moved down into contact with the material and until the stirrers are again retracted from the kiln. Each stirrer R is of sullicient width to stir the material all the way across the widtl. of the trough shaped receptacle farmed by the cavities H of the various cars G. lVhen the stirrers are in- 'serted in the kiln, the doors Q are closed, notches Q being formed in the edges of these doors to receive the stem portions S of the stirrers. After a brief stirring period not suiciently prolonged to heat the stirrers R to a destructive temperature, the doors Q, are opened, the' gears W are rotated in a clockwise direction to retract the stirrers to the position shown in Fig. 5, after which the doors Q are again closed. The stirrers are left out of the kiln chamber long enough for them to cool off as much as may be necessary before the stirring operation is repeated.

Vhile in accordance with the provisions of the stat( tes we have illustrated and described, the* est forms of our invention now known to us, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed ,without departing from the spirit of our invention as set forth in the appended claims and that certain features of our invention may sometimes be used to advantage without a corresponding use of other features.

Having now described our invention, what we claim as new and desire to secure by Letters Patent, is:

1. In a continuous tunnel kiln the combination with they kiln chamber and track rails therein, of means for transporting material through the kiln chamber comprising a train of cars each comprising a metallic underframe with track engaging wheels mounted therein and a refractory superstructure formed with a trough-like cavity in its upper face which ext-ends longitudinally of the car and unites with the corresponding cavities of the other cars ous trough extending the length of the train.

2. In a continuous tunnel kiln the combination with the kiln chamber and track rails therein, of means for transporting material through the kiln chamber comprising a train of cars each comprising a metallic underframe with track engaging wheels mounted structure formed with a trough-like cavity in its upper face which extends longitudinally of the car and lunites with the corresponding cavities of the other cars to form a continuous trough extending the length of the train and stirrers extending down- Ward from the roof of the kiln into said trough.

3. In a continuous tunnel kiln the combination with the kiln chamber and track rails therein, of means' for transporting material through the kiln chamber comprising a train of ears each comprising a metallic underframe with mounted therein and a refractory superstructure formed with a trough-like cavity in its upper face which extends longitudinally of the ear-and unites with the corresponding cavities of the other ears to. form a continuous trough extendin the length of the train and Huid cooled stlrrers extending downto form a continutherein and a refractory super` track engaging wheels ward from the roof of the kiln into said trough. y y

4. In a continuous tunnel kiln, the combination with the kiln chamber, of-a travelling platform for transporting material through said chamber and fluid cooled devices mounted in the kiln chamber and engaging and agitating the material on the platform as the latter is advanced.

5. In a continuous tunnel kiln, the combination with the kiln chamber, of a. travelling platform for transporting material through said chamber, of stirrers engaging said material and agitating the latter as the platform is advanced a'nd hollow supports for said stirrers extending through the wall of the kiln chamber andexter'nally connected into a cooling fluid circulation system.

6. In a continuous tunnel kiln, thecombination with the kiln chamber, of a travelling support for,I transporting material through the kiln chamber, of a series of rotatable stirrers movable into and out of the kiln chamber and adapted when in the latter to engage and stir the material on said support.

7. In a continuous tunnel' kiln, the combination with a. kiln chamber formed with a series of apertures in its roof, of a travelling support for transporting material through sai A.i chamber and a series of material stirrers movable into and outof said chamber through 'said roof and means for rotating said stirrers.

8. In a contmuous tunnel kiln, the combmation with a kiln chamber formed with a series of apertures in its roof, of a travelling support for transporting material through said chamber and a series of material stirrers movable into and out of said chamber through said roof and a. common means for rotating said stirrers as they are being inserted and while in said chamber.

Signed at Cleveland in the county of Cuyahoga and State of Ohio this twentyseventh day of June A. 11.1922.

PAUL A. MEEHAN. HARRY-M. ROBERTSON. 

